Characterization of chicken gizzard calcyclin and examination of its interaction with caldesmon

Using a procedure developed to purify calcyclin from mouse Ehrlich ascites tumor cells calcyclin was purified from smooth muscle of chicken gizzard. Chicken gizzard calcyclin bound to phenyl-Sepharose in a calcium dependent manner as did mouse EAT cells and rabbit lung calcyclin but appeared to be more acidic than its mammalian counterparts as revealed by ion exchange chromatography on Mono Q. Chicken gizzard calcyclin bound ⁴⁵Ca²⁺ on nitrocellulose filters and exhibited a shift in electrophoretic mobility on urea-PAGE depending on Ca²⁺ concentration. Crosslinking experiments with BS³ showed that chicken gizzard calcyclin was able to form noncovalent dimers. As indicated by a decrease in maximum tryptophan fluorescence emission of caldesmon (about 14% at 1:1 molar ratio) and displacement of calmodulin from its complex with caldesmon, chicken gizzard calcyclin binds caldesmon. This binding was, however, much weaker than that of calmodulin and could not influence the interaction of caldesmon with actin. In consequence, calcyclin was unable to reverse the inhibitory effect of caldesmon on actin-activated Mg²⁺-ATPase activity of myosin in the presence of Ca²⁺.     

PHI-1 interacts with the catalytic subunit of myosin light chain phosphatase to produce a Ca(2+) independent increase in MLC(20) phosphorylation and force in avian smooth muscle

In avian smooth muscles, GTPgammaS produces a Rho kinase mediated increase in PHI-1 phosphorylation and force, but whether this correlation is causal is unknown. We examined the effect of phosphorylated PHI-1 (P-PHI-1) on force and myosin light chain (MLC(20)) phosphorylation at a constant [Ca(2+)]. P-PHI-1, but not PHI-1, increased MLC(20) phosphorylation and force, and phosphorylation of PHI-1 increased the interaction of PHI-1 with PP1c. Microcystin induced a dose-dependent reduction in the binding of PHI-1 to PP1c. These results suggest PHI-1 inhibits myosin light chain phosphatase by interacting with the active site of PP1c to produce a Ca(2+) independent increase in MLC(20) phosphorylation and force.     

Factors related to gizzard shad and the threadfin shad occurrence and abundance in Florida lakes

Gizzard shad Dorosoma cepedianum were collected in 23 and threadfin shad D. petenense were collected in 22 of the 60 Florida lakes sampled. Logistic regression equations were 94% effective for predicting gizzard shad occurrence from chlorophyll and lake surface area, and 84% effective for predicting threadfin shad occurrence from lake surface area and lake volume inhabited (PVI). Occurrence of both shad species was related positively to lake size. In lakes where gizzard shad or threadfin shad were collected, shad density and biomass of both shad species were related positively to chlorophyll. Gizzard shad populations were generally vulnerable to predation in lakes, with the per cent of gizzard shad ≤200mm L _T values exceeding 60% with few exceptions. Effects of gizzard shad and threadfin shad on fish community dynamics may be confined to relatively large (>100 ha) and fertile (chlorophyll >20–30μg l⁻¹) Florida lakes.     

The feeding mechanisms of Lynceus (Crustacea: Branchiopoda: Laevicaudata), with special reference to L. simiaefacies Harding

Although generally assumed to be filter feeders, branchiopod crustaceans of the laevicaudatan genus Lynceus O.F. Müller, 1776 possess no filters and do not collect food by filtration. Investigated species of these bivalved, multi‐limbed animals have basically benthic habits and collect particulate food, mostly detritus, by scraping or sweeping it from surfaces with suitably armed trunk limbs. L. simiaefacies Harding, 1941, known only from a desert pool in Yemen, has trunk limbs that are armed with particularly robust scrapers and much of the complexity of these limbs and their armature is related to the collection and manipulation of detrital food by mechanical means. Material collected by scrapers borne distally on the more anterior limbs – although the anteriormost is very lightly armed – is swept posteriorly and dorsally, assisted by the armature of the more proximal endites, towards the posterior end of a deep food groove, whence it is passed anteriorly by the substantial gnathobases of the trunk limbs. The necessary movements of the trunk limbs are facilitated by a system of intrinsic muscles that enable individual endites to be moved independently – a remarkable specialized feature of a phyllopodial appendage. Before it enters the food groove, collected material is at all times confined to a narrow median chamber, or cage, between the two sets of opposed trunk limbs that extends over most of the anterior limbs – which are the largest. Each cage wall serves as a screen, covering the limbs of its side and is made up of long setose screening setae that superficially resemble coarse filter setae, and arise from the more proximal endites of most of the anterior trunk limbs. The screens prevent collected material from entering the inter‐limb spaces into which water flows during each cycle of trunk limb movements, where its presence would be disastrous. They do not interfere with the spines of the proximal endites that can protrude between them. The screens do not extend to the extreme posterior end of the trunk limb series where a complex and dense array of specialized spines of the short posterior trunk limbs completes the task of sweeping food material into the food groove. Material is passed anteriorly along the food groove by the trunk limb gnathobases and the small but robustly armed maxillules to the mandibles. Although constructed on the basic, boat‐like, branchiopod plan, in contrast to those of most particle‐feeding branchiopods whose mandibles have a broad masticatory surface, those of Lynceus have a masticatory surface that is narrow and elongate in the antero‐posterior plane. Interestingly, while the number of ‘teeth’ into which this surface is elaborated is few in most species of the genus, inviting comparison with a similar attribute in the Notostraca, L. simiaefacies has more numerous, smaller teeth. Although following the branchiopod plan, the mandibular musculature appears to have its own distinctive features but remains to be investigated in properly fixed material. At its distal extremity the oesophagus is differentiated into a small but complex gizzard, of which there appears to be no parallel in any other branchiopod order. This is described for the first time. Although provided with natatory antennae, species of Lynceus also employ their trunk limbs as organs of propulsion. In L. gracilicornis (Packard, 1871) the carapace valves can gape to more than 90°, which allows the trunk limbs to make a contribution to propulsion in a manner akin to that of the Anostraca. In this respect the Laevicaudata appears to stand in contrast to the Spinicaudata, in most species of which the trunk limbs contribute little or nothing to locomotion. More information is needed on representatives of both orders, which have received little study as living animals. Brief comments are made on the systematic position of the Laevicaudata, about which much remains to be resolved. © 2009 The Natural History Museum. Journal compilation © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 513–541.     

Fish gut microbiota analysis differentiates physiology and behavior of invasive Asian carp and indigenous American fish

Gut microbiota of invasive Asian silver carp (SVCP) and indigenous planktivorous gizzard shad (GZSD) in Mississippi river basin were compared using 16S rRNA gene pyrosequencing. Analysis of more than 440 000 quality-filtered sequences obtained from the foregut and hindgut of GZSD and SVCP revealed high microbial diversity in these samples. GZSD hindgut (GZSD_H) samples (n=23) with >7000 operational taxonomy units (OTUs) exhibited the highest alpha-diversity indices followed by SVCP foregut (n=15), GZSD foregut (n=9) and SVCP hindgut (SVCP_H) (n=24). UniFrac distance-based non-metric multidimensional scaling (NMDS) analysis showed that the microbiota of GZSD_H and SVCP_H were clearly separated into two clusters: samples in the GZSD cluster were observed to vary by sampling location and samples in the SVCP cluster by sampling date. NMDS further revealed distinct microbial community between foregut to hindgut for individual GZSD and SVCP. Cyanobacteria, Proteobacteria, Actinobacteria and Bacteroidetes were detected as the predominant phyla regardless of fish or gut type. The high abundance of Cyanobacteria observed was possibly supported by their role as the fish''s major food source. Furthermore, unique and shared OTUs and OTUs in each gut type were identified, three OTUs from the order Bacteroidales, the genus Bacillariophyta and the genus Clostridium were found significantly more abundant in GZSD_H (14.9–22.8%) than in SVCP_H (0.13–4.1%) samples. These differences were presumably caused by the differences in the type of food sources including bacteria ingested, the gut morphology and digestion, and the physiological behavior between GZSD and SVCP.     

Regional difference in the responsiveness to the inductive influence of the gizzard mesenchyme among the endoderms of various small intestinal segments of the chick embryo

The differentiation of the endoderms of duodenal, jejunal and ileal segments of the small intestine of 6 day old chick embryos cultured in recombination with the gizzard mesenchyme of 6 day chick embryos was examined. Only the duodenal endoderm differentiated in a mesenchyme-dependent fashion into gizzard-like mucous epithelium forming tubular glands that expressed no sucrase-antigen, while jejunal and ileal endoderms tended to become the sucrase-antigen-positive epithelium most likely according to their developmental fates. The analysis on the differentiation of the duodenal and gizzard endoderms in the presence of various digestive-tract mesenchymes confirmed that the duodenal endoderm had the tendency to differentiate into intestine-type and was different from the gizzard endoderm, which showed the differentiation tendency into gizzard-type. Thus, among the segments of small intestine, only the endoderm of duodenum that was situated next to the gizzard was found to have an ability to respond to the inductive influence of the gizzard mesenchyme and to change its developmental fate.     

Population structure and food habits of white crappie Pomoxis annularis Rafinesque in a turbid Oklahoma reservoir

We assessed population structure and food habits of white crappie Pomoxis annuluris Rafinesque in Lake Carl Blackwell, a turbid reservoir in north-central Oklahoma, U.S.A. White crappie [ n = 8549; total length ( t.l. ) mean = 147 mm, s.d. = 28 mm, range = 73–445 mm] were collected with gillnets, frame nets, and hoop nets. Proportional stock density was 2, as 97% of the fish were under 200 mm t.l . Relative stock density was 96, 2, 1, and 1 for 'stock-quality', 'quality-preferred', 'preferred-memorable', and 'memorable-trophy' lengths. Total annual mortality rate was 54% for fish older than 2 years. Growth was poor and lower than the Oklahoma-Arkansas regional averages ( P <0.01). Relative weights were 79, 86, 106, 109, and 123 for fish in the stock-quality, quality-preferred, preferred-memorable, memorable-trophy, and trophy size categories. Ephemeroptera nymphs were an important dietary component for fish 150 mm t.l. or smaller. Gizzard shad Dorosoma cepedianum (Lesueur) was a major forage item, especially for fish greater than 150 mm t.l. ( P <0.01). Empirical information on prey availability indicates that the white crappie population is forage limited and that gizzard shad are not available in appropriate sizes or sufficient numbers to sustain the predator population. Poor fish condition, slow growth, and high mortality are probably the result of inadequate forage.     

Comparison of Atrogin-1/MAFbx mRNA Expression in the Gizzards of Egg- and Meat-Type Chickens

We examined atrogin-1/MAFbx mRNA expression in the smooth muscle of gizzards from egg- and meat-type chickens. Gizzard weight relative to body weight was significantly lower in the meat-type chickens than in the egg-type at 14 d of age. In contrast, the level of atrogin-1/MAFbx mRNA in the gizzard was significantly higher in the meat-type chickens than in the egg-type chickens. Thus atrogin-1/MAFbx mRNA expression in the smooth muscle of the gizzard was higher in meat-type chickens than in egg-type chickens, in contrast to its expression in the skeletal muscles.